port" consideration. The A.E.C. plan was to proceed with the preparation of the final report, to fix up minor errors in the draft, and to ignore the more general criticisms of the study's con- troversial p{obability analysis. The final report's accident-probability esti- mates would be virtually identical with those of the August, 1974, draft. T HE conclusion of the draft ver- sion of the Rasmussen Report- that meltdown accidents were unlikely to have catastrophic effects-reversed all previous A.E.C. analyses. The dis- covery that only a few people might be killed-not the thousands or tens of thousands estimated in earlier govern- ment studies-brought great comfort to the A.E.C. and the nuclear indus- try. The section of the report most heavily criticized by independent ex- perts, however, was the short technical appendix that supposedly demonstrated this welcome resul t. Even before the objections were filed-indeed, before the draft was released-Rasmussen knew, he later told me, that this ap- pendix "needed more work," though he did not mention it at the A.E.C. press conference at which the draft report was made public. Correcting its deficiencies had not been possible prior to publication, he informed me, be- cause of the schedule set by the A.E.C. In any event, Rasmussen and his staff were not the authors of this section of the report. It was written by Winston Little, an engineer employed by West- inghouse-a leading American reac- tor manufacturer-who was on loan to the Reactor Safety Study. The American Physical Society, an association of professional physi- cists, gave the A.E.C. the most de- tailed criticism of the draft report's assessment of the consequences of meltdown accidents. Earlier in the year, the A.P .S. had set up a special panel to review the genera] topic of nuclear-reactor safety. Frank von Hippel, a theoretical physicist who had worked at a number of universities and national laboratories, played an impor- tant role in organizing the study. The members spent August of 1974 to- gether at the A.E.C.'s Los Alamos laboratory, in New Mexico. The draft version of the Reactor Safety Study was published that month, and they made an attempt to review key parts of it. Von Hippel was immediately struck by the study's finding that meltdown accidents would not have particularly dire consequences, and he and his col- leagues reviewed the basis on which the health effects of a meltdown were calculated. To do so, they did their own "back of the envelope" calcula- tions; that is, they took the Rasmussen Report's estimates of how much radio- active material would be released dur- ing a hypothetical meltdown and then calculated by hand-rather than by computer, as the Rasmussen group had done-what the effects would be on the population downwind of the plant. They came up with fatality estimates far greater than those of the Rasmussen group, and they soon knew why. The group's cal- tJ culations, they discov- ered, contained basic er- rors. The A.E.C.'5 fa- tali ty estimates, for example, considered the radiation dose to the downwind population only during the first twenty-four hours after an accident. The fact is that the radioactive ce- sium (137Cs) contained in the fallout from an accident-a substance that would be among the principal sources of injury-has a half-life of thirty years, and for de- cades to come it would expose the population, over an area too wide to be evacuated, to its harmful effects. The most serious injuries from cesium ex- posure would be forms of cancer which would not show up until years after the accident. The A.P .S. re- viewers also found that the draft Rasmussen Report entirely neglected inhaled radioactivity in its calculations of the expected incidence of lung cancer among the exposed population, and that it made assumptions that greatly underestimated the incidence of thyroid tumors that would result from the inhalation of radioactive iodine, which would also be contained in the fallout produced by a meltdown. The writing of the A.P .S. report became a touchy political process, be- cause the findings about the validity of certain calculations in the Rasmussen Report were not the only negative ones; other subgroups of the panel were drafting reports critical of other key aspects of the Commission's nu- clear-safety program. They found, for example, that the computer methods used to predict the performance of emergency cooling systems had not been satisfactorily verified. Von Hippel wanted the A.P .S. report to be candid and objective. "The reactor-safety de- bate was very hot," he said recently. 61 "Some of the people on the committee became concerned about the impact of our report on the reactor-safety con- troversy-that it could be the end of nuclear power." The members dis- cussed how they could "cushion the blow," and say "some positive things" to tone down the negative message in the report they were drafting. A lot of "negotiated language" and "wea- se] words" were used in the end, mem- bers of the panel have stated privately. One standard method for handling bad news in official reports is to bury it deep inside, where most readers- and most news re- porters, especially- will not delve. A few soothing sentences at the beginning, intend- ed to characterize the wri ters' findings for popular consumption, help to effect this strat- egy. Accordingly, the A.P .S. report, released in April of 1975, began with a sum- mary paragraph that had a positive tone-one that the members could agree on, despite their acknowledg- ment of weaknesses in the official "proof" of nuclear-plant safety. They could do so because, technically, the summary said almost nothing. "In the course of this study, we have not un- covered reasons for substantial short- range concern regarding risk of acci- dents in light-water reactors," the introductory paragraph states. This sentence, which was included in the official press release for the report, seems reassuring. All i t really says, though, is that the panel did not dis- cover a reactor that was in imminent danger of a meltdown. The sentence figured prominently in most news re- ports about the A.P.S. study; they overlooked the ambiguous qualifying phrase "short-range" and described the study as a resounding confirmation of A.E.C. claims about reactor safety. The news accounts also generally failed to note another heavily "negoti- ated" sentence, on the same page of the report, which says, politely, that the review panel didn't believe the Rasmussen Report's probability esti- mates. "Based on our experience with problems of this nature involving very low probabilities, we do not now have confidence in the presently calculated absolute values of the probabilities," the panel wrote. The Rasmussen group knew, of course, about the sig-